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    <p><code>int *findFactors(int, int);</code> line says you wanna return pointer from this function (it's better to use asteriks closer to the type name: <code>int* moo();</code> - this prevents misunderstandings i think).</p> <p>If you wanna dynamically change function argument (which is better way than just return pointer), you should just use argument as if you have this variable already.</p> <p>And the last your mistake: <code>malloc(X)</code> allocates <code>X</code> <strong>bytes</strong>, so if you want to allocate memory for some array, you should use <code>malloc(N * sizeof(T));</code>, where <code>N</code> is the size of your array and <code>T</code> is its type. E.g.: if you wanna have <code>int *a</code>, you should do this: <code>int *a = (int*) malloc(10 * sizeof(int));</code>.</p> <p>And now here's your code, fixed (as for me):</p> <pre><code>#include &lt;stdio.h&gt; #include &lt;stdlib.h&gt; int findFactors(int, int*); int main(int argc, char **argv) { int numToFind, *factors = 0, cnt = 0; do { printf("Enter a number to find the factors of: "); scanf("%d", &amp;numToFind); } while (numToFind &gt; 100); cnt = findFactors(numToFind, factors); printf("%d has %d factors.\n", numToFind, cnt); return 0; } int findFactors(int N, int* factors) { if (!factors) factors = (int*) malloc(N * sizeof(int)); int count = 0; for (int i = 2; i &lt; N; i++) { if (N % i == 0) { factors[count++] = i; printf("%d is factor number #%d\n", i, count); } } return count; } </code></pre> <p><strong>Note:</strong> do not forget to initialize your pointers any time (as i did). If you do want to call function, passing a pointer as its argument, you must be sure it has value of <code>0</code> at least before function call. Otherwise you will get run-time error.</p>
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    1. PONewbie question. How to pass pointers in to a function in C?
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    1. USshybovycha
    1. USshybovycha
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    1. COMemory returned by `malloc` is not zero initialized. You should add a `memset(factors, 0, sizeof(int) * N);` otherwise the values will be undefined.
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      1. USSylvain Defresne
 

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